In general, chromatography involves the flowing of a mobile phase over a stationary phase to effect separation. To speed-up and enhance the efficiency of the separation, pressurized mobile phases were introduced. For example, in carbon dioxide based chromatography systems, carbon dioxide or a carbon dioxide mixture is used as the mobile phase solvent in a supercritical or near supercritical fluid state. To keep the carbon dioxide in a supercritical or near supercritical fluid state the chromatography system is subjected to a predefined pressure. Most often, a back pressure regulator is employed downstream of the chromatography column to maintain the predefined pressure. After the mobile phase mixed with the separated sample passes through the back pressure regulator, the supercritical, near supercritical or liquid carbon dioxide turns into gas phase carbon dioxide. The gas phase carbon dioxide is removed from the liquid eluate by passing through a gas-liquid separator.
Gas-liquid separators are effective at removing gases, but also impose detrimental effects on the detection and any subsequent fraction collection. For example, inertial separators require a comparatively large vessel volume (compared to its liquid volume) into which the aerosolized eluent can expand. This comparatively large vessel can result in cross contamination of fractions. Additionally, these separators typically rely on the formation of liquid droplets that impinge onto the walls/surface of the vessel that ultimately drain to the bottom by flowing along the wall/surface of the vessel. This can result in a significant amount of dispersion and possibly cross contamination of separated samples. Similarly, cyclone separators require the use of an applied centrifugal force which in some applications is variable and frequently inconsistent. For example, there is a sizeable difference between gas and liquid velocities which can lead to the re-entrainment of liquid from the wall. In addition, the dispersion of liquid droplets onto the walls/surface of the vessel that ultimately drain to the bottom of the vessel, can result in cross contamination of fractions. As such, there remains a need for more robust and efficient gas-liquid separators and separation methods to enhance fraction collection yields and purity.